Being caught committing a drugs offence here in Beijing is an 825–1 shot. Odds like those surprise even the International Olympic Committee.

The head of its medical commission, Professor Arne Ljungqvist, said a week ago that the three positive tests from 2,203 returned at that time was a "quite low" figure because "usually we have dozens". Since then the number of doping controls conducted has almost doubled to 4,133 but there have still only been two more positive tests. With the athletes at these Olympics going stronger, higher, faster across the board, should we be suspicious?

Victor Conte certainly thinks so. The man who, as the founder of Balco, was the architect of the biggest athletics drugs scam in history — or at least the biggest ever to be exposed — said on Monday that he believes the anti-doping culture of some National Olympic Committees and teams leaves much to be desired.

"When [race] times begin falling like rain, questions arise, especially when the record-setters are from countries such as Jamaica and other Caribbean nations where there is no independent anti-doping federation," he wrote in a letter to the New York Daily News.

Some teams definitely have form. The entire weightlifting team of Greece was banned from these Olympics after 11 of its 14 members tested positive for steroids in March.

So even at odds of 825–1 we should not perhaps be too taken aback that the biggest name to have been caught doping is Fani Halkia, winner of the 400m hurdles for Greece in Athens. The former Olympic champion's story fits Conte's description well: having come back from retirement to lower her personal best by 1.22sec in the 2004 semi-finals, she won gold by a half-second margin. The IOC has now engaged lawyers to prosecute her coach, George Panagiotopoulos, another of whose athletes has also recently tested positive for steroids.

The strangest thing is that three of Beijing's four other drugs cheats did not test positive for an even vaguely sophisticated substance. A North Korean double medallist in shooting used beta-blockers; a Vietnamese gymnast had taken medication used to control PMT; and the cyclist María Isabel Moreno flew home to Spain as soon as she had provided her specimen, knowing how soon the IOC would turn up the EPO in her system. It seems an almost contemptuous lack of competence in the field of sporting deception.

It is not yet known for what Lyudmila Blonska, the latest to fall foul of the procedures, has been caught. But these Games' heptathlon silver medallist is a repeat offender who served a two-year ban for using the proscribed steroid stanozolol in 2003. Her silver-medal performance at the world championships last year aroused the suspicions of Kelly Sotherton — the Briton had finished third behind Blonska.

The IOC, though, points to its low hit rate with a cheerful smile. "I think quite many recent events have shown that we are rather on the heels of those who try to cheat," said Ljungqvist last week. "The situation has been improved. "My interpretation is that it is a feature in the increased awareness in the sports population that doping is unaccepted, [it is] unacceptable to compete in the Games if you dope yourselves. I feel that the figures are encouraging rather than anything else."

Ljungqvist's organisation obviously has the most to lose with every positive test, and others might say the evidence suggests that the cheats are staying one step ahead of the system. Quite apart from the incompetence of the officials conducting the procedures — the bruises on Chris Hoy's arms as he won his third gold medal on Tuesday show how unfamiliar they are with the cartography of veins — observers have a right to wonder why there have been no positives for the latest designer drug, slow-release EPO.

The IOC says it is employing a reliable test for the third-generation version of the drug after its detection was trialled at this year's Tour de France. But here is another statistic: the 2008 Tour also threw up five positive tests, a race in which there were fewer than 200 riders as against more than 10,000 athletes in the Olympic village. Does that add up?